Isolate antithrombin III (heparin cofactor) from Cohn Factor IV by affinity techniques using such materials as sepharose-heparin. Develop means to inactivate HAA virus with little loss of biological activity in the heparin cofactor preparation. Study the interaction of heparin cofactor with heparin in relation to the in vivo effectiveness of the complex in dogs. Finally, perform a clinical evaluation of the product in man.